This document discusses how virtualization and cloud computing can improve disaster recovery management. It begins by describing traditional disaster recovery approaches like dedicated and shared models that require tradeoffs between cost and speed of recovery. It then explains how cloud computing provides virtualized disaster recovery mechanisms that can offer lower costs, faster recovery times through replication of virtual servers, and improved scalability and flexibility. The document concludes that cloud computing is well-suited for disaster recovery as it allows organizations to scale resources as needed and achieve more reliable continuity of operations at lower costs than traditional approaches.

1. International Journal of Research in Advent Technology, Vol.2, No.5, May 2014
E-ISSN: 2321-9637
Virtualizing Disaster Recovery Management Based On
397
Cloud Computing
Ms.Shital V. Bahale 1 , Prof. Dr.Sunil Gupta 2.
M.E.(II Year)- Department of Computer Science and Engg. P.R.M.I.T.R, Badnera-Amravati 1,
Assistant Professor- Department of Computer Science and Engg. P.R.M.I.T.R, Badnera-Amravati 2
Email: shitalbahale@rediffmail.com1 , sunilguptacse@gmail.com2
Abstract - Almost from the beginning of widespread
adoption of computers, organizations realized that
disaster recovery was a necessary component of their
information technology plans. Business data had to
be backed up, and key processes like order entry,
billing, payroll and procurement needed to continue
even if an organization’s data center was disabled
due to a disaster. Growing reliance on crucial
computer systems means those even short periods of
downtime can result in significant financial loss, or in
some cases even put human lives at risk. Many
business and government services utilize Disaster
Recovery (DR) systems to minimize the downtime
incurred by catastrophic system failures.
Cloud computing provides the third leg of a disaster
recovery plan that is essential for business continuity.
Cloud-based storage services take advantage of
Internet access to deliver reliable, low-cost online
storage, helping you to bounce back from a full-scale
data center disaster for less than the cost of a
dedicated online storage solution.
Virtualization is the means of ushering in a new,
productive era of cloud computing, driven by this
need for cost management and increased agility.
Virtualization can also provide the basic building
blocks for your cloud environment to enhance agility
and flexibility. This paper delineate how
virtualization of cloud computing can be used to
address the concerns resulting in improved computer
infrastructure that can easily be restored following a
natural disaster ,reduced expenses, improved
scalability, better performance and is easier to
manage.
Index Terms - Disaster Recovery requirements;
Dedicated and shared DR models; Virtualization;
Cloud based DR mechanisms;
1. INTRODUCTION
A key challenge in providing DR services is to
support Business Continuity (BC), allowing
applications to rapidly come back online after a
failure occurs. By minimizing the recovery time and
the data lost due to disaster, a DR service can also
provide BC, but typically at high cost. Cloud
computing platforms are well suited for offering DR
as a service due to their pay-as-you-go pricing model
that can lower costs, and their use of automated
virtual platforms that can minimize the recovery
time after a failure[1,2].
A typical DR service works by replicating application
state between two data center’s if the primary data
center becomes unavailable, then the backup site can
take over and will activate a new copy of the
application using the most recently replicated data[8].
Virtualization is the foundation for an agile, scalable
cloud and the first practical step for building cloud
infrastructure [11]. Virtualization abstracts and
isolates the underlying hardware as virtual machines
(VMs) in their own runtime environment and with
multiple VMs for computing, storage, and
networking resources in a single hosting
environment. These virtualized resources are critical
for managing data, moving it into and out of the
cloud, and running applications with high utilization
and high availability [14].
Virtualization is managed by a host server running a
hypervisor software, firmware, or hardware that
creates and runs VMs[17]. The VMs are referred to
as guest machines [6,9].
Virtualization also provides several key capabilities
for cloud computing, including resource sharing, VM
isolation, and load balancing. In a cloud environment,
these capabilities enable scalability, high utilization
of pooled resources, rapid provisioning, workload
isolation, and increased uptime.

2. International Journal of Research in Advent Technology, Vol.2, No.5, May 2014
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In this paper we explore how virtualized cloud
platforms can be used to provide low cost DR
solutions that are better at enabling Business
Continuity. In the first section this paper discusses
data recovery requirements , second section explores
traditional approaches to disaster recovery then in
third section describes data recovery mechanisms
and fourth section describes cloud computing
mechanisms for data recovery lastly it concludes with
how organizations can use cloud computing to help
plan for both the mundane interruptions to service—
cut power lines, server hardware failures and security
breaches—as well as more-infrequent disasters.
2. DATA RECOVERY REQUIREMENTS
This section discusses the key requirements for an
effective DR service. Some of these requirements
may be based on business decisions such as the
monetary cost of system downtime or data loss, while
others are directly tied to application performance
and correctness.
2.1 Recovery point objective (RPO)
The RPO of a DR system represents the point in time
of the most recent backup prior to any failure.
2.2 Recovery time objective (RTO)
The RTO is an orthogonal business decision that
specifies a bound on how long it can take for an
application to come back online after a failure occurs.
This includes the time to detect the failure, prepare
any required servers in the backup site (virtual or
physical), initialize the failed application, and
perform the network reconfiguration required to
reroute requests from the original site to the backup
site so the application can be used.[7]. Having a very
low RTO can enable business continuity, allowing an
application to seamlessly continue operating despite a
site wide disaster.
2.3 Performance
For a DR service to be useful it must have a minimal
impact on the performance of each application being
protected under failure-free operation. DR can impact
performance either directly such as in the
synchronous replication case where an application
write will not return until it is committed remotely, or
indirectly by simply consuming disk and network
bandwidth resources which otherwise the application
could use.
2.4 Consistency
The DR service must ensure that after a failure occurs
the application can be restored to a consistent state.
2.5 Geographic Separation
It is important that the primary and backup sites are
geographically separated in order to ensure that a
single disaster will not impact both sites. This
geographic separation adds its own challenges since
increased distance leads to higher WAN bandwidth
costs and will incur greater network latency.
Increased round trip latency directly impacts
application response time. Asynchronous techniques
can improve performance over longer distances, but
can lead to greater data loss during a disaster.
Distance can especially be a challenge in cloud based
DR services as a business might have only coarse
control over where resources will be physically
located.
3. TRADITIONAL DISASTER RECOVERY
APPROACHES
In traditional disaster recovery models—dedicated
and shared— organizations are forced to make the
trade-off between cost and speed to recovery.
3.1 Dedicated disaster recovery model
In a dedicated model, the infrastructure is dedicated
to a single organization. This type of disaster
recovery can offer a faster time to recovery compared
to other traditional models because the IT
infrastructure is duplicated at the disaster recovery
site and is ready to be called upon in the event of a
disaster. Although this model can reduce RTO
because the hardware and software are preconfigured,
it does not eliminate all delays. The process is still
dependent on receiving a current data image, which
involves transporting physical tapes and a data
restoration process. This approach is also costly
because the hardware sits idle when not being used
for disaster recovery. As illustrated in Figure 1, data
restoration can take up to 72 hours including the tape
retrieval, travel and loading process[3].
Dedicated
Data Restore
6 hrs or less 4-72hrs
Interrupt Recovery
Declare H/W Setup S/W Setup Data Restore

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Figure 1. Time To Recovery using a Dedicated Infrastructure
3.2 Shared disaster recovery model
In a shared disaster recovery model, the infrastructure
is shared among multiple organizations. Shared
disaster recovery is designed to be more cost
effective because the off-site backup infrastructure is
shared among multiple organizations. After a disaster
is declared, the hardware, operating system and
application software at the disaster site must be
configured from the ground up to match the IT site
that has declared a disaster, and this process can take
hours or even days. In addition, the data restoration
process must be completed as shown in Figure 2,
resulting in an average of 48 to 72 hours to
recovery[3].
Shared
Declare H/W Setup S/W
Data Restore
Setup
Interruption Recovery
Declare H/W Setup S/W Setup Data Restore
Figure 2. Time To Recovery using a Shared Infrastructure
With dedicated and shared disaster recovery models,
organizations have traditionally been forced to make
tradeoffs between cost and speed. As the pressure to
achieve continuous availability and reduce costs
continues to increase, organizations can no longer
accept tradeoffs. Any downtime reflects directly on
their brand image, and customers view any
interruption of key applications such as e-commerce,
online banking and customer self-service as being
unacceptable. As a result, the cost of a minute of
downtime may be thousands of dollars.
4. DR MECHANISMS
Disaster Recovery is primarily a form of long
distance state replication combined with the ability to
start up applications at the backup site after a failure
is detected. Backup mechanisms operating at the file
system or disk layer replicate all or a portion of the
file system tree to the remote site without requiring
specific application knowledge [6].
The use of virtualization makes it possible to not only
transparently replicate the complete disk, but also the
memory context of a virtual machine, allowing it to
seamlessly resume operation after a failure however,
such techniques are typically designed only for LAN
environments due to significant bandwidth and
latency requirements [4, 9].
DR services fall under one of the following
categories:
4.1 Hot Backup Site
A hot backup site typically provides a set of mirrored
stand-by servers that are always available to run the
application once a disaster occurs, providing minimal
RTO and RPO. Hot standbys typically use
synchronous replication to prevent any data loss due
to a disaster. This form of backup is the most
expensive since fully powered servers must be
available at all times to run the application, plus extra
licensing fees may apply for some applications.
4.2 Warm Backup Site
A warm backup site may keep state up to date with
either synchronous or asynchronous replication
schemes depending on the necessary RPO. Standby
servers to run the application after failure are
available, but are only kept in a “warm” state where it
may take minutes to bring them online. This slows
recovery, but also reduces cost.
4.3 Cold Backup Site
In a cold backup site, data is often only replicated on
a periodic basis, leading to an RPO of hours or days.
In addition, servers to run the application after failure
are not readily available, and there may be a delay of
hours or days as hardware is brought out of storage or
repurposed from test and development systems,
resulting in a high RTO. It can be difficult to support
business continuity with cold backup sites, but they
are a very low cost option for applications that do not
require strong protection or availability guarantees.
5. MECHANISMS FOR CLOUD DISASTER
RECOVERY
While cloud computing platforms already contain
many useful features for supporting disaster recovery,
there are additional requirements they must meet
before they can provide DR as a cloud service.
5.1 Network Reconfiguration
For a cloud DR service to provide true business
continuity, it must facilitate reconfiguring the
network setup for an application after it is brought
online in the backup site[10]. Public Internet facing
applications would require additional forms of
network reconfiguration through either modifying
Min 4 hrs Min8-24 hrs Min 4 hrs 4 -72hrs

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DNS or updating routes to redirect traffic to the
failover site.
5.2 Security & Isolation
The public nature of cloud computing platforms
remains a concern for some businesses. In order for
an enterprise to be willing to fail over from its private
data center to a cloud during a disaster it will require
strong guarantees about the privacy of storage,
network, and the virtual machine resources it
uses[12,13].
5.3 VM Migration & Cloning
Current cloud computing platforms do not support
VM migration in or out of the cloud. VM migration
or cloning would simplify the failback procedure for
moving an application back to its original site after a
disaster has been dealt with. This would also be a
useful mechanism for facilitating planned
maintenance downtime[4][16].
Cloud computing offers an attractive alternative to
traditional disaster recovery. “The Cloud” is
inherently a shared infrastructure a pooled set of
resources with the infrastructure cost distributed
across everyone who contracts for the cloud service.
This shared nature makes cloud an ideal model for
disaster recovery. Even when we broaden the
definition of disaster recovery to include more
mundane service interruptions, the need for disaster
recovery resources is sporadic. Since all of the
organizations relying on the cloud for backup and
recovery are very unlikely to need the infrastructure
at the same time, costs can be reduced and the cloud
can speed recovery time[5].
Because the server images and data are continuously
replicated, recovery time can be reduced dramatically
to less than an hour, and, in many cases, to minutes—
or even seconds. However, the costs are more
consistent with shared recovery.
Figure 3. Cloud based approach to disaster recovery
Cloud computing based on virtualization, takes a
very different approach to disaster recovery. With
virtualization, the entire server, including the
operating system, applications, patches and data is
encapsulated into a single software bundle or virtual
server[15]. This entire virtual server can be copied or
backed up to an offsite data center and spun up on a
virtual host in a matter of minutes.
Since the virtual server is hardware independent, the
operating system, applications, patches and data can
be safely and accurately transferred from one data
center to a second data center without the burden of
reloading each component of the server. This can
dramatically reduce recovery times compared to
conventional (non-virtualized) disaster recovery
approaches where servers need to be loaded with the
OS and application software and patched to the last
configuration used in production before the data can
be restored.
The cloud shifts the disaster recovery trade-off curve
to the left, as shown below. With cloud computing
(as represented by the red arrow), disaster recovery
becomes much more cost-effective with significantly
faster recovery times.
Figure 4. Cloud Disaster Recovery Trade-offs
The cloud makes cold site disaster recovery
antiquated. With cloud computing, warm site disaster
recovery becomes a very cost-effective option where
backups of critical servers can be spun up in minutes
on a shared or private cloud host platform.

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One of the most exciting capabilities of disaster
recovery in the cloud is the ability to deliver multi-site
availability. SAN replication not only provides
rapid failover to the disaster recovery site, but also
the capability to return to the production site when
the DR test or disaster event is over.
One of the added benefits of disaster recovery with
cloud computing is the ability to finely tune the costs
and performance for the DR platform. Applications
and servers that are deemed less critical in a disaster
can be tuned down with less resources, while
assuring that the most critical applications get the
resources they need to keep the business running
through the disaster.
6. CONCLUSION
With pay-as-you-go pricing and the ability to scale
up as conditions change, cloud computing can help
organizations meet the expectations of today’s
frenetic, fast paced environment where IT demands
continue to increase but budgets do not.
Virtualization also eliminates hardware
dependencies, potentially lowering hardware
requirements at the backup site.
By coordinating disaster recovery and data back-up,
data loss can be reduced and reliability of data
integrity improved. In future focus is on using fault
tolerant server hardware within virtualized cloud
environments to reduce management complexity to
sustain the high service levels.
Virtualizing disaster recovery start up can also be
automated for lowering recovery times after a
disaster.
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